Field of the Invention
The present invention relates to a separation apparatus for separating a composite substrate formed from a first substrate and a second substrate joined together into the first substrate and the second substrate.
Description of the Related Art
In an optical device fabrication process, a light emitting layer formed from an n-type semiconductor layer and a p-type semiconductor layer configured from gallium nitride (GaN) or indium gallium phosphide (InGaP) or else aluminum gallium nitride (AlGaN) is stacked on the surface of a sapphire substrate or an epitaxy substrate of silicon carbide having a substantially disk shape with a buffer layer interposed therebetween. Further, optical devices such as light emitting diodes or laser diodes are formed in regions partitioned by a plurality of streets formed in a grid-like pattern on the light emitting layer to form an optical device wafer. Then, the optical device wafer is divided along the streets to fabricate individual optical devices.
Meanwhile, as a technology for improving the luminance of an optical device, a fabrication method called liftoff is disclosed in Japanese Patent Laid-Open No. 2004-72052. According to the fabrication method, to a light emitting layer formed from an n-type semiconductor layer and a p-type semiconductor layer stacked on the surface of a sapphire substrate or an epitaxy substrate of silicon carbide which configures an optical device wafer with a buffer layer interposed therebetween, a relocation substrate of molybdenum (Mo), copper (Cu), silicon (Si) or the like is joined with a bonding metal layer of a metal (AuSn) or the like interposed therebetween. Then, a laser beam of a wavelength (for example, 257 nm) which is absorbed by the buffer layer is irradiated upon the epitaxy substrate from the rear face side to break the buffer layer, and the epitaxy substrate is exfoliated from the light emitting layer while the light emitting layer is relocated to the relocation substrate.